Integrative Marine Ecology Department, Stazione Zoologica Anton Dohrn, Center of Benthic Ecology-Villa Dohrn, Punta S. Pietro, 80077 Ischia, Naples, Italy; Department of Biology, University of Naples Federico II, Via Cinthia, 80126 Naples, Italy.
Integrative Marine Ecology Department, Stazione Zoologica Anton Dohrn, Center of Benthic Ecology-Villa Dohrn, Punta S. Pietro, 80077 Ischia, Naples, Italy.
Sci Total Environ. 2018 Jul 1;628-629:375-383. doi: 10.1016/j.scitotenv.2018.02.065. Epub 2018 Feb 13.
Corallinales (Rhodophyta) are high Mg-calcite macroalgae and are considered among the most vulnerable organisms to ocean acidification (OA). These sensitive species play fundamental roles in coastal systems as food source and settlement promoters as well as being involved in reef stabilization, and water carbonate balance. At present only a few studies are focused on erect calcifying macroalgae under low pH/high pCO and the contrasting results make difficult to predict the ecological consequences of the OA on the coralline algae. In this paper the physiological reasons behind the resistance of Jania rubens, one of the most common calcareous species, to changing ocean pH are analysed. In particular, we studied the photosynthetic and mineralogical response of J. rubens after a three-week transplant in a natural CO vent system. The overall results showed that J. rubens could be able to survive under predicted pH conditions even though with a reduced fitness; nevertheless physiological limits prevent the growth and survival of the species at pH6.7. At low pH (i.e. pH7.5), the maximum and effective PSII efficiency decreased even if the increase of Rubisco expression suggests a compensation effort of the species to cope with the decreased light-driven products. In these circumstances, a pH-driven bleaching phenomenon was also observed. Even though the photosynthesis decreased at low pH, J. rubens maintained unchanged the mineralogical composition and the carbonate content in the cell wall, suggesting that the calcification process may also have a physiological relevance in addition to a structural and/or a protective role. Further studies will confirm the hypotheses on the functional and evolutionary role of the calcification process in coralline algae and on the ecological consequences of the community composition changes under high pCO oceans.
珊瑚藻门（红藻门）是高镁方解石大型藻类，被认为是对海洋酸化（OA）最敏感的生物之一。这些敏感物种在沿海系统中发挥着重要作用，既是食物来源和定居促进者，也是珊瑚礁稳定和水碳酸盐平衡的参与者。目前，只有少数研究集中在低 pH/高 pCO2 下的直立钙化大型藻类，而对比结果使得难以预测 OA 对珊瑚藻的生态后果。在本文中，分析了最常见的钙质物种之一 Junia rubens 对不断变化的海洋 pH 值具有抗性的生理原因。特别是，我们研究了 J. rubens 在天然 CO2 喷口系统中移植三周后的光合作用和矿物学响应。总体结果表明，J. rubens 即使在适应能力降低的情况下，也能够在预测的 pH 条件下生存；然而，生理极限阻止了该物种在 pH6.7 下的生长和生存。在低 pH（即 pH7.5）下，最大和有效 PSII 效率降低，即使 Rubisco 表达增加表明该物种为应对光驱动产物减少而做出补偿努力。在这种情况下，还观察到了由 pH 驱动的白化现象。尽管在低 pH 下光合作用减少，但 J. rubens 保持细胞壁的矿物成分和碳酸盐含量不变，这表明钙化过程除了具有结构和/或保护作用外，还可能具有生理相关性。进一步的研究将证实关于钙化过程在珊瑚藻中的功能和进化作用以及在高 pCO2 海洋中群落组成变化的生态后果的假说。
